wallet: provide valid values if invalid estimate mode passed

Co-authored-by: Murch <murch@murch.one>

test/functional/wallet_basic.py

@@ -263,7 +263,7 @@ class WalletTest(BitcoinTestFramework):
             assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",  # max value of 1008 per src/policy/fees.h
                 self.nodes[2].sendmany, amounts={address: 1}, conf_target=target, estimate_mode=mode)
         for target, mode in product([-1, 0], ["btc/kb", "sat/b"]):
-            assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
+            assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"',
                 self.nodes[2].sendmany, amounts={address: 1}, conf_target=target, estimate_mode=mode)
 
         self.start_node(3, self.nodes[3].extra_args)
@@ -434,7 +434,7 @@ class WalletTest(BitcoinTestFramework):
                 assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",  # max value of 1008 per src/policy/fees.h
                     self.nodes[2].sendtoaddress, address=address, amount=1, conf_target=target, estimate_mode=mode)
             for target, mode in product([-1, 0], ["btc/kb", "sat/b"]):
-                assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
+                assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"',
                     self.nodes[2].sendtoaddress, address=address, amount=1, conf_target=target, estimate_mode=mode)
 
             # 2. Import address from node2 to node1